Since the inception of this PPG in 1982, the overall goal of this program has been to achieve an understanding of the long-term regulation of arterial pressure and the consequences of high blood pressure. The unifying hypothesis of the present grant centers on the concept that the kidney controls the long-term level of arterial pressure and when genetically predisposed salt intake can importantly influence kidney function and the structure and function of the systemic vasculature. Project 1 will utilize Dahl salt-sensitive rats (SS) to study how a high salt diet may stimulate excess production of reactive oxygen species (ROS) in the renal medullary thick ascending limb (mTAL) leading to reduction of blood flow to the renal medulla, reduction in sodium excretion and hypertension. Project 2 hypothesizes that during the early phase of saltinduced hypertension an inflammatory process is initiated by infiltrating macrophages that produces angiotensin II (ANGII) that stimulates the production of ROS thereby increasing the severity of hypertension and renal injury. Project 3 will search for a mutation in one of the cytochrome P4504A genes (CYP4A) that is the underlying genetic defect in the SS rat that plays an important causal role in the impaired pressurenatriuresis and the development of hypertension. Project 4 examines the permissive role that ANGII plays in maintaining normal vascular reactivity and how defects in the SS renin allele lead to increased oxidative stress and impaired vascular relaxation. Project 5 focuses on the microcirculation and the mechanisms that control and alter organ and tissue perfusion in hypertension and the impact that reductions in ANGllstimulated O2 inhibit the VEGF signaling pathway leading to microvessel rarefaction and inhibition of angiogenesis that is found in the SS rat. Each of these projects utilize unique genetic rat strains (consomic, congenic, and transgenic) that provide the trait of interest and a genetically defined control strain. Hypertension affects more than 50 million Americans and remains largely uncontrolled in 75% of patients in North America leading to an increased incidence of stroke, heart, and renal disease, that contribute to escalating health care costs. The program reflects a long-standing experience of shared ideas in a synergistic environment aimed toward advancing our understanding of hypertension and the identification of novel targets for drug design that may better control this disease.